Automatic telephone system.



8. D. WILLIS.

AUTOMATIC TELEPHONE SYSTEM- APPLICATION mm sgrT. l9. l9!!- Patnted Oct.7,1919.

4 SHEETS-SHEET l.

v v V fnuezz zuf Bernard H. Wills.

B. D. WILLIS. AUTOMATIC TELEPHONE SYSTEM.

- APPLICATION man SEPT. 15, 1911. 1 18,004. Patented Out. 7,1919.

4 sums-snzzr 2 Bernbrdfl 74/1755;

' 1B. 0. wl usfj' "AUTOMATIC uamoursysr-m- Arrucmon man SEPT us m:

1,318,004. -gmmed 0015x1919.

4 SHEE S-SHEET 4.

, a 1 Barnard ZZZ 3.171115.

' and a resident .of Chicago, county of Cook,

rammed? osmicn.

D. \YILLIS, OF CHICAGO, ILLINOIS, ASSIGNGR Ti) AUTOMATIC ELECTRIG m ccaSpecification of Letters Patent.

COMPANY, OF CHICAGO, ILLINOES, A CORFQEATIQN F ILLINOI",

' AUTOMATiC TE'LEJPHUNE SYSTEM.

Patented @ch '7, ism.

Application filed Septemlicr 19, ieiv. Serial No; 192,125.

To 3117mm it may concern.

it known that I, BERNARUD. WILLIS, a citizen of the-United States ofAmerica,

and State, of Illinois, have invented certain new and usefulImproven'ients in- Automatic Telephone Systems, of which the followmg isa specification.

My. invention relates to automatic telephone systems, and involves anumber of separate features. many of which are applicalole to automaticsystems in general, but which are especially valuable in a particulartype of 1 system which I term a mixed service s stem. The distin uishingcharacteristics 0 such systems toget e2? with the improvementsprovidedby my invention, their fuctions and operation,- will-lie described fullyhereinafter, reference being had to the accompanying drawings; 7

In the drawings, Figure 1 is a schematic diagram or trunking layout of atypical mixed service system; Figs. 2-, 3 and l are circuit drawings ofthe essential features of the system shown. ill-Fig. 1;-while Fig. 5

is a detail of a portion of the ringing equipment. 1 y e Reierrmgto-Flg. 1, an automatic exchange such as the one shown. within therectangle and indicated by the reference character suitable for a smalltown of perhaps thousand inhabitants, which may be the center of a wellpopulated rural community. YVithin the town and Within a limited radiusoutside there maybe a number of privatij or'individuallines, such as theline 2, and'a number of four party lines,

such the line 1. Personslivingat re moter points are not. usually givensuch, a high qual ty OfSBI'VlCG, bem-ggcnerally connectcd in largernumbers'ou so called farmer lines or rural lines. Two such lines as thisare th e eight party lines 3 and While only a fe w linesare shown it\willhe' understood that there will be many more radiating in; alldirections-fron'l the exchange X as a. common center. j

still greater distances there may be other small centers of population,each with its system of telephone lines diverging from a central.exchange; and there will inevitahl y ger, centers of population orcities angle of telephonic communication. The smaller towns may besupplicd with telephone service by mixed service automatic systems suchas the one disclosed herein, or they may have small manual exchanges.Either large multiple manual switch boards, or moder full automaticsystems may he used in tl e cities, depending upon the stage ofdevelopment that has been reached bf, the company operating in tlieparticular community. Whatever the char actor of the equipment used,these other ere changes may be connected with the exchange X by means oftrunk lines, two or which, extending to two different exchanges, areshown in the drawing. There may be many more exchanges than the twoshown, and a plurality of trunk lines extending to each, but since thetrunks may all be included in two classes, manual and automatic, thetwoshown will he suflicient for purposes of illus' tration. Thus the trunkline 5 is one of a group of trunks connecting the exchange X with thesmall manual exchange Y, while the trunk line 6 is one of a group whichextends to the large automatic exchange Z. All lines entering theexchange whether "individual lines, party lines, or trunk lines,terminate in individual line switches or trunk selectors, These switchesare indicated in the drawing by reference characters C to C", inclusive.The line switches have common access to' a group of trunk linesextending to first selector switches, 'thr which are the], selectors E:E and have the well known function 005' extenc in calling lines to idleones of these selectors "The banks of the selector-sure all multipledtogether and form terminals of trunk lines extendingto connectorswitches which have access tocalled lines. .Thcconnectors are dividedinto two groups, whether the numher of lines in the system exceeds thecapacity of asingle. group of connectors Thus the connectors F and F arincluded in one group, while connectors F and F are included in thesecond group. The trunk lines terminating in one group of conncctorspreferably extend from the first level rangement of these latter isfollows: The s trunk.l

upper or tenth level in one or bothof connectorsis reserved forthe-groups oi particular level or levels On account of a switchingoperation neces sary to be. performed at theconnectors on calls to otheiautomatic exchanges, anitlns switching operation is most "convenient atof trunk lines or a group of trunk occupy the same level with 1nd1---However, for con 4 trunk lines terminate in the "ninth level of lines,=certain e .Withone of the oonnecto J an e mentioned that the necessitof provi group offconnectors.

Inorde'r to take care of the eightparty rresponding levels in both gmmpsof connectors, designated in the drawing' as the sixth and eighthlevels, are multipled together; This is necessary on ac-' count of theselective ringing and it may mg for selectively ringing the substationson the eight party lines is the prime reason, or dividing the connectorsinto two groups.

e connectors of each group are provided means for selectin any one, ofthe four standard frequencies of ringing current 'as used. in we systeequipment .siss oeiated 1' groups is adapted.

substation 'a,

The ringing- 9 give thebell at a the other group of connectors isadapted to gs separated by a short interval repeated at longerintervals.

I v methods eight 'stations on a line may be selectively signaled.

understood .that

line 2 partylines such asthe line 1. v

11 any automatic system which contains party lines, means mustordinarily be pro: to signal other For this purtwo of erence charactersI and the four ch are indicated by ref tion Wlll l briei' description ofthe apparatus Wlll be'as'sumed that the manual ringer 13, c0

having-the windings 15 and 16. hook I? is provided with "a locking lever19- are separated to whl stations are tions A H? ,and H, and a commonsingle motign ringing switch, indicated by reference char- 'acter I. Thering back switches may be accessible to subscribers linesvia the thirdlevel of the first selectors as shown.

It is believed that foregoing descr pthe general layout of i0 circuit intl be given,

after-which t e operation will be explained in detail.

The line shown in Fig. 2 ductors-30 and 31 is an the substations A -toinclusive, nccte-d in bridge thereof in the usual manhese eightsubstations only subis shown complete, the other seven ply by a ringerand condenser bridge across the line., The substation A is similar tothe substation shown in the application of John Erickson, Serial N o. edNovember 10, 1916, except that 1: e circuits are modified for use in acommon battery system. It comprises essentially the receiver 10,transmitter'll, switch hook 12, eiiseiuli and induction coil he switchwhich 13 adapted to hold th an intermediate is removed. III

e switch hook in the intermediate position "of position when thereceiver the switch hook contact springs 20 and 21 termine whether ornot the line is in. use.

e line is idle thelocking lever 19 is renectingthe' transinit terllacross the line feature of the substation is fully disclosed in theapplication and shunt springs 17 are shown herein.

be similar to the one the patent to Dicker No. 29,654 e ringers at thedifferent sub- This calling device may disclosed in Of 1910.

frequencies of ringing current, there bein two ringers which are adaptedto respond to each frequency. Thus tl gers at substations A and Arespond "to. the 16 cycle ringing current while th and current, etc. esubscribers'at substation 1 and. A however, only respond when a whilethe subrespond -s1gnals.' the exchange the line conductors 30 terminatein the individual line of Erickson tuned to respondto different I I eringers at substa- A respond to 33 cycle ringing misses switch C; Thisline switch may be of the general type diselosed in the British patentto James No. 26,3 1 of 1966; heing,hoWever, of the particular pe shownin ll. S. Letters Patent No. 1.015.690, granted January 19, L912, toll'ranl: h ewt'orth. .ilhrougxh the mediiun of line in 1 G the po tyline shown is given 'acc a plurality of selector switches as h readybeen explained.

The line switch similar line swi fies are controlled in their trunkselecting; operations by means of a master switch D. The master switchl) is of the general type of master switch disclosed in the abovementioned British patent to dairies lle. 261,301. of 190th being.however,

more nearly 0 the particular type disclosed in the British pa nt tolrlartin #1419 of 1910. is well lrnown the function of the master switchis to nn-iintain the plungers of all the idle lino switches which itcontrols in position before the terminals of an idle trunk line. I

one of the trunk lines to which the line switch C has' access is shownin the drawing extended to the first selector E which may be of thegeneral type of selector switch disclosed in U. S. Letters Patent No.815,321,

06, to Keith, Erickson granted iii larch a side switch and private andErickson,

magnet are omitted, however, and the cir cults ere modified inaccordance with the two wire system of control. The operation of theline switch C and the selector switch E will he described during theprocess of explaining the establishment of connections.

At the right of '2 three sets of bank contacts, one in each of threelevels, are

shown ins-being accessible to the Wipers of' the selector E. From thefirst: level contact set comprising conductors 95, 96 and 97 extend to aconnector (not shown) in the first connector group of theexohange. Thesecond level contact sel comprising hank contacts 86, 87

and 88 the terinina-lof a trunk line comprism ""comtiuctors 932 93 and9% which" extends to the connector (Fig. 0) in the second connectorgroup. A third trunk line comprising the conductors 98, 99 and 100extends from the third level contact set machine Q may he magnet H2 andwipers H2 and Q and a plurality of bank contacts 83, 8% and 85,

' the automatic .exchang e Z.

conductors for each'ol these trunk hues, two;

quency selecting ringing equipment Ill. The busy signaling andis of theusual type found in other well known automatic telephone systems, The.

freouenev selectino switch S is individual to 1 W o the connector andcou'iprises e stepping wh ch switch S, end intermittent common to theexchange are adapted to be operated for the purpose oi. selecting theringing cunent' generator required to signal a desired subscriber.- Theringing equipment IR- is common to the sec ond group of connectors. Asshownherein it consists essentially of a relay 150 con trolled by a. twosegment interrupter,which adapted- When energized to connect the.

generators AC to AC, inclusive. simultaneously to the four generatorleads extending to the frequency selecting switches associ-..

ated with connectors of the second group, In the deenergized position ofthe relay 150 these four generator leads are connected. to the positiveterminal of a booster battery...

In Fig. 5 there is shown at modification of.

the ringing equipment 'IR which to'be used in connection with the firstgroup of connecto It Will be seen that the only dii'ierence between thetwo sets of ringing equipment is in the constriution of the. in}.terrupters employed. T he interrupter shown inl ign has but a singlelive segment while the other intcrrupterhas two live segments, thusproviding evidently for the one and two hell ringin Atthe right of thereis shown a fragmentary portion of the bank of corn nector Fi The lowersets of banks are line contacts in the seventh, eighth, ninth andspending levels. There is nothing new in the b-enk wiring except thewiring of the private bank contacts on the trunking levels. Consideringfirstthe tenth level in which the groups of automatictrunlis are termihated it has been assumed arbitrarily that there are three groups oftrunks withthree trunks in each of the first two groups and four trunksin the last. Each group qf trunks extends to 'a dilfcrent a'utoinaticexchange, the last group including thetrunk comprising normal conductors200 to 203, inclusive, being the group whichextends to illiere are fourL2G tenth levels while the upper-sets of contacts are private or testcontacts in the cor-re:

line conductors and two private or test condoctors. lhe division of thetrunk lines into groups is deterniined by the inclusion of i aresistance in the second test conr luctonof the last trunk of each'n'roup. This isclearly shown in the drawing and the function of g theresistance will he explained 'lully here?v ll G..\Vl1'1l1 Q"Uf the ninthlevel in.

after. which terminate thegroups of trunk line extending to manualexchanges is' somewhat beingfurther 1 1n mechanical constr itrion shownin the 'iaten't/to Keith, l lricksonand .IKZOdlfiGCl, however, inorderdifferent. Each of these trunk lines hasonl a group except The wiring ofthe remaining levels is standard, the second test contact of eachcontact set being left dead. 1 he normal conductors 200 to 203,inelusive,

extend to and terminate in a re- M. This repeater comprises essentiallya repeating coil R and the relays 225 to 229, inclusive, whose functionsand operation will be described. ductor trunk line 6 extends to thedistant automatic-exchange Z where it terminates in the repeating coil Rrepeater M. The repeater M except for a slight circuit change necessaryexchange to the main exchange are extended by way of conductors whichterminate in an individual line switch. Calls in the reverse directionwhich originate at the main exchange are extended to the trunk lineshown by way of conductors 262, 263 and 261 which may terminate in aselector level or in some level of a group of rotary connectors. Thesecompleted at the mixed service exchange by wayr'f conductors 241 and 242Which-terminate inthe line switch C (Fig. 1

The ring back swfich H" is a vertical and rotary directively .cont'olled switch similar l to the switch Erickson, ,o."815,176, thecircuits being v to adapt the s W-itch to the two wire system of controland modified to enable the switch to perform its function of a ring backapparatus. .The switch H" has bht two dicated by reference characters330 and 331 and only the live lower levels of line contacts are used.The private or @test contacts are omitted entirely.

he ringing switch. I is a single motion rotary switch and may be of anysuitable construction; it being necessary only to provide connectionsfor, the wipers which permit their continuous forward moven'lent asshown in the' patent to Lamb N 0. 1,193,160, granted August 1, 1916. Inits preferred form and as show n diagran'imatically herein it com manualexchanges on associated with the April 13, 1915. Calls and comprisesvthe inmates in the usual the call the switch hook wipers inother,thereby bridging receiver 10 permitted to rise to its final "tactsprings 21,22 and 23 gagement and the transmitter By tl t ripleconstruction and are continuously in clusive, may be the same generatorswhich are shown in Fig. 3. The wiring of so much of the bank of the ringback switch H as is in use and the wiring of the bank of ringing switchI is shown complete and will be explained in the description of theoperation.

It has not been thought necessary to show any of the trun lines whichextend to account of the fact that the equipment associated with thesetrunk lines is old and is in part shown in Fig. 2' of the drawings.onsidering for example the trunk line which is accessible to connector Fby way of the seventh set of contacts in the. ninth level, the normaleonductors 207, 208 and 209 extend to and terminate in an individualline switch indicated in Fig. 1 by the reference character C This lineswitch is similar in all respects to the line switch C", the circuits ofwhich are shown in detail in Fig. 2. It will be seen then that in so faras the exchange equipment is concerned these trunk lines are similar tothe party line shown in Fig. 2 conductors 30 and 31. At the manualexchange each trunk line terdrop, jack, and cut oil relay. Manualequipment of this kind is old and well known and need-not beillustrated.

-Having described briefly the apparatus involved in the system itsoperation will now be considered. The operation of the on localconnections will first phone number of the latter substation being i2842. hen the calling subscriber at sub station Aremoves his receiver toinitiate 12 is permitted to rise about half way where it is held by thelockinglever 19. I his position ot the switch hook contact springs 20and 21 .are

separated while contact springs 21 and 22 are brought into engagementwith each the condenser 14, and secondary winding 15 across thetwoconductors of the line. The calling subscriber will now place thereceiver to his ear in order to determine whether ornot the line is inuse. i No conversation being hea'rd the locking lever 19 is now releasedby hand, whereupon the switch book 12 is position. Conare now in en- 11and'primary .coil are bridged line in parallel with the receiver. 1eclosure of the transmitter bridge a winding 16 of the induction acrossthe flow of current is established in the wind ing of the line relay 32of line switch Ctas follows: ground at G inner set of cut oii' springs,line conductor 31, primary'winding 16utransmitter 11, contact springs23, 22

I and 21, line conductor 30, outside set of cut mature the line relay3-2 oii springs and thc windings of the line reand from the groundedpole of battery.

By the engagement of bank springs L0 and 4-3, respectively, withcontacts M and d7, the line conductors 30 and 31 are extended by way oinormally closed contacts of the switching relay 58 to the impedance coil51 and the line relay 50 of the selector E. The line relay 50 isaccordingl energized over the closed line circuit, inc uding subsstation A, and upon attracting its armature closes a circuit for theslow'acting release relay Upon energizing-relay 5'2 corn-r plctes allOl(l11l I circuit tor the line switch (I which may be traced asfollows: ground working contact of armature 60. and the. said armature,conductor 61, contact 45, bank spring 11, holding winding 35, andteri'ninal as to battery. The line relay is slmv'acting in order that itmay retain its armature in operated position until after the abovetraced circuit has been completed. A branch of the holding, circuitextends by way of conductor 37 to multiple test contacts in the banks ofthe connector switches which have access to the line of substation A,

Where by a ground potential upon these test contacts the lineis madebusy. By the engagement of bank spring :2 with Contact as, the masterswitch'l) is operated in the usual manner to advance the plungers of allthe remaining idle line switches into position before thetcrminals ofthe next idle trunk line. Q

The foregoing trunk selecting operations have occurred automatically inresponse to the removal of the receiver, The calling subscriber will nowoperate his calling de-- vice in accordance with the first digit in thedesired number, or the digit 2, thereby twice separating theimpulsemnings 18 and producing two interruptions in the circuit of theline relay 50. In response to these interruptions of its, circuit, theline relay 5 1) is decnergized a couple oftirnes and at eachdecnergization transmits an impulse from ground G through the lowresistance slow acting relay and the vertical magnet let to at, inclu-80, 81 and 82 into engagement set of bank contacts in the second level.Near the end of its stroke the rotary magnet 56 in series, slow actingrelay 52 remaining in operated position notwithstanding theinterruptions in its circuit produced by the nion'i'entarydeene'rgizations of theiline relay. The vertical magnet 56 responds tothe impulsestransmitted by the line relay and operates to raise theswitch shaft and the wipers 80, 81 and 82 until the latter stand opeposite: the second horizontal level of bank The relay 53 is energized inseand being slow contacts. ries with the vertical magnet,

acting, retains its arinatures in operated position during the series ofimpulses. At

the first upward movement of the shaft the 0H normalsprings 59 areclosed, thereby completing an initial energizing circuit for Y thestepping relay which extends from the. grounded conductor 61 by way,of-the lower armature of relay' 53, the ofl normal springs 59, and thewinding of the said relay 5a tobattery. Upon energiz1ng,',the relay 54;looks itself independent of relay 53 at its upper armature and at itslower armature prepares a circuit for the rotary magnet 55 which is heldopen duringthe vertical movement lay 53. In addition to those describedthe slow acting relay 53 has a new function, in that at its upperarmature it connects the lower low resistance winding of impedance coil51 in parallel with the upper winding. The lower winding of relay 51 isprefeu' ably non'inductive and its inclusion in the line reduces theresistance and impedance oi the. control circuit '1icluding .thelinerelay 50, thereby greatly improving the op eration of the selectorswitch in response to impulses. On longrural telephone lines slow actingrelay 53 denergizes at the end of the. vertical movement of the switch avcircuit is completed for the rotary magnet 55 extending from thegrounded conductor 61, by way of the springs controlled by the lowerarmature of relay 53, the lower annature of relay 5e and thewinding ofthe retary magnet 55 to battery. Upon energim ing, the rotary magnetadvances the wipers with the first of the switch by the reopens itsinterrupter contact and thereby hreal's the locking circuit of thestepping relay 54, Upon the deenergization of the stepping relay, the,circuit of the rotary magnet is in turn broken and the rotary" "thecircuit of the more, the steppingv relay completes the circuit 0f therotary magnet as before and the switch wipers are advanced to the secondset of contacts. Since the stepping relay 54 and the rotary 'niagneteach interrupt other it-i'vill be'seen that the switch Wipers willcontinue tobe ad vanced step v wiper 81 engages busy or grounded testcontacts, an idle trunk line is reached, assumed to be the test contact87, the test wiper 81 will nd -no ground potential and the steppingenergized; Instead the. switching relay 08 which until now hasbeeufiiisu, l 105 connectrelay 54 will not be short circuited isenergizedover a circuit ,which may 'be traced briefly as follows:

(31, winding of the switching relay 58, interrupter contact of therotary magnet o'lf normal springs 59, and" the winding-of the steppingrelay 54 to battery. Relay 58 is sufficiently high in resistance torender the relay 5+ inoperative. Upon energizing, relay 58 opens acontact in the circuit of the release magnet -57 at its lower armature;at its upper armature shifts the connection of the test wiper 81 fromits upper'to its lower terminal; and at.,its two inner arinaturcsdisconnects the line conductors and 31 from their connection in theselector E and extends them by way of wipers 80 and 82, hank congroundedconductor tacts 86 and 88, conductors 92 ,and ill, and

' contactsv controlled by relay 1'01 and 102 to fol lows:

the windings of the impedance coil 153 and the line relay 103,respectively, of the con ncctor F. .The line relay 1 03 is accordingly;energized over the calling subscribers loop and closes the usual circuitfor the slow acting release relaylOl. 'lhis'lattei' relay, uponenergizing, completes a hohlingcircuit for .the selector E and the lineswitch C"- as ground at G, spring 121 and its resting contact, armature125) and its working contact, winding 152 of induction coil conductor93, bank contact 87, n ip -r 81,

- and the upper armature of relay 58 and its working contact to junctionpoint 02-, where the circuit divides, one branch extending by way ofthe. previously traced circuit through relays 58 and 54 to battery andthe other branch oining the conductor 61 over which it supplies holdinggi'ound'to the line switch C.

The calling subscriber may now operate his calling device in.:u-cordance with the second digit, 8 of the called number,therebyproducing a series of interruptions in; the circuit of the line relay103. Tu response to these intcrruptit ins of its circuit the line-relay103 is dei nergized a corresponding number of lllllvfi'tlml at eachdeiinegization transmits an impulse to the vertical magnet 11.0 over thefollowing path: ground atG, wiper 142 of the frequency selector S,conductor by .step long as the test,

l/Vhenfa test contact associated with 'ofg impulses as usual.

. of the switch the sive, stand opposite the eighth horizontal The relay105 is level of bank contacts. energized iirsei-ies with the verticalmagnet and retains its armature during the serles the right hand windingof the impedance coil 153 in multiple with the left hand winding inorder to reduce the resistance and impedance of the control circuit ofthe line relay 103, this being the same'operat-ion that was described inthe case of the selector E. I addition then-clay 105 closes a circuitfor the private nagnet 108 as follows: ground at (i, armature 131,spring 132, and the winding of the private magnet 108 to battci'v.

lllilgllttdtlifi' are deenergized, the latter pertormingits wellknown-function of advancing the side switch wipers 113, 111 and 115 totheir second position.

The third digit 1 of the desired number may now be called in the samemanner as thepmccding digits. 5 A series of four interruptions'is nowproduced in the circuit of the line relay 103 and the said relayaccordingl y is again dei nergized momentarily a number of times.Now-however, the side switch wiper 111 having been advanced to itssecond.position,.impulsesare trai'isniitted to the rotary magnet: 111 asfollows: ground at G", wiper 142 of the frequency selecting switch S.conductor 154, armature 126 and its resting contact, armature 128 andits working contact, winding of the relay 105. resting contact of spring131 spring, winding of the rotary niagiieelll, and the side switch wiper111 in second position to battery. In response to impulses over ,theabove circuit the rotary, magnet is operated to rotate the connectmrshaft until the wipers 1.70 to 173, inclusive, arrive at the fourth setof contacts in' the eighth level. 'lhe slow acting relay 105' isenergized as -before. and performs the crations including theclosurelo't the circuit n lignet 108. At theend of of the privatc theI'Oitlt'lUiP't) .ie switch the relay 105 and the private magnetdeinergize and the side tacts tnt 1e eighth level At its upper arma Xt. theend of the vertical movement relay 105 and the private same ops assumed--that the called and the said to third position,- therefore, a i uitminate in the individual line switch C 1) in the. serhe manner thatthenorniel. eon duotorsiBT, 38 and terminate in the in (lividuel lineswitch C (Fig. 22 When thesides iteh, the connector is advancedcompleteil for, the out. of? or holrlingwinning; of the called lineSWllZCil C traced follows: ground while and Hie side switch Wiper in.hird posifion, lower private wiper 171, (.OE'KiUCiZOL ill), ELli-(l theout be Wilding of line switch G to battery. The out of? armature of i eCilllflll line ewitchvis thereupon attracted to clear the called line ofits normal lJt ery' and ground connections; Ground G" also tends to themultiples or" the te'si; cont; with which the Wiper 171 in erigag omen zand the ealleql iine'is thus made lousy remaining connectors in thegroup.

The Wipers of the connector having been advanced into engagemeni withthe set bank contacts associated with the-desired which may he celledline the next operation is esfialr,

lishment of 'a signaling circuit for ringing the hell zit/the desiredstation on the line. In order to accomplish this the frequencyselectingswitch S must be operated. The calling subscriber accordinglywill now operate his calling device for the final digit 2 of the callednumber with the resell; lint two interruptions ere producecl in thecircuit of thelinereley103. The en equehijde'nergizetions of the linerelax; new pi'lmhiee two current impulses in the cir-enit .oi the stepping magne 11 2 of the fre'queney selector S.

This .eireuii; may be traced. as follows:;

ground at G, wiper 1 92, eonuotor 15 i, allllllllllfl 128 end itsrestingcontact, armeture 128 and its Working Contact, Winding of relay 105Winding of the stepping; magnet LL? and the side switch Wiper 114- inthir-zi posit-ioii to hettery In response to the two impuieeereoeiredover the illhf'bve circuit the "Q. gne 1- 112 is operaied to advance theerslBeml 1&3 two seeps, whereby they are brought into engagement withthe thirdcont acs ietheir respeoeive hanks. At the first moyement of thewiper M2 ground G is aliseonnectel from comiuetor 15 Since the relay 105energized in series with the magnet l ii however, the armature of relay.is not ilieoonnecleil from ground, but the movement of the Wiper 1.42has effect on the operation for armetare 1:26 is temporarily suppliedwith ground from by l,"ll'lili3lll"fi 131, 132 and its workingrontwst.Relay 105 also closes the circuit of the private? n' egnel; 108 as usualeni me private magnet is eherei'ore energlide iclurihg *Jhe operation ofthe frequency; ee line wip '5 H2 and L73. At the encl of the finalseries oi" impulses the relay and the private magnet 108 areclenergized'.

' Sta-ion A, norm respond to the 33 172 and 173 from/ rupter H 2 i l)gene or lead. o roqueney eommior mz'iich 5i, eomluaor I i nornml con$2.. he armature, immature l is, 1 ing eonzact upper Winding of the cutoff we My 107, Tillie. swlhzh w'per 13, in third position, to battery.By the operation of i'he ringing iniierrupter iii; ringing: cw'reni if?:21 8 the generator All is oroje .ted intermitl line to signal the 3trueiion of the ina rapidly suemipiilses i by e r period. oi? e eraltimes the length of zhe interval hem impuises. When, howeve, the ringingcurrent is cut off from fie line by the (leenerg izetion of relay thegenerator lezul sting Contact oi .2111 1 eonneefied to the positive poleof he hoes-rezhettery shown just ehove lo the right 0 '1 lay 150. Thering oil? r ay 107 is so cljustedihzi't it is not fe lay 'ihe rin,current While the re tion is on the hook. When he .3 removed, however.the relay m2, is energizezi either by current {T0311 the mliin batteryin series with the generator thee in use or current from the mainbattery in series with the hoos'zer battery.

The ringer at subst rioh A. is tuiie to cycle and since the sub ah th isetetion has been nstructed m scriberi answer when a two oe'l ringreceived he will 110W remove his enol'immedietely release the Switchhook to its final or talking position. The ring out off relay 10? isthereupon energizecl oi once irrespective of the posibion oil: theringing interrupter Til? and establishes a 1 remit for lie. as folio refgrout '5 i riormei spriiig 1%? -21 j. the 1 meet engaged thereby(broegghi'into engagement at he first if? Ward movement of the switchshaft), time 139 and its working contact enol' die lower winding of i-hering out releyi'f)? to battery. as a furher result of its en moan relay10'? disconnects the line uyper Winding er from the geiiereior lead M4.-enci e-ormee them instead to the upper and lower i182. taikiiipeondnetori-i, respeeriveiy. T1'3KASl'2x1l1-- ter ourreira for ihe calledsubstation now supplied as follows: ground G 01% norsaid armature,

therewith. and the mal spring 147 and the contact engaged thereby,armature 139 and its working contact, the lower winding of the answeringbridge relay 102, resting contact of spring 119 and the said spring,working contact of armature 138 and the said armature, arma'; ture 141and its resting contact, Wiper 173, normal conductor 212 to ant throughthe substation A 172, resting contact of armature 140.

contact, spring 117 and its resting contact, upper winding of theanswering bridge re lay 102, and the winding 151 of induction coil P tobattery. The current 'flow over the its armatures 122 and 124 reversesthe incoming line conductors 92 and 94 as regards their connection tothe windings of impedance coil 153 and the line relay 103. addition, attheworking contact of spring 125, controlled by armature 124.,the uppercondenser is connected to complete the talking circuit. lhe reversal ofthe line conductors described is useful in certain cases for controllinga meter or coin collecting device associated with the calling line, butsince there is nothing new in this operation no measured service deviceshave been shown.

he required connection has now been established. Talking current issupplied to the transmitter at the called substation through thewindings of relay 102 as already explained; while talking currentfor-the transmitter at the calling substation 1s 1 the windings of relay103 supplied througl The path for the and impedance coil 153.

voice currents through the several switches, has been drawn inheauy'lmcs and will be readily understood without further explanation.

When the conversation is finished both subscribers will replace theirreceivers. By the replacement of the receiver at substation A the linerelay 102- of connector Fa is dcenergized, followed by thedeenergization' of the slow acting release relay 104-. A circuit isthereupon established for the re-'v lease magnet 10!) as follows: groundat (i spring 121 and its resting contact, armature 12!) and its restingcontact, otl' normal spring H 0 and the contact in engagement windingot' the release magnet 100 to battery. By the energization of therelease magnet the switch shaft and the side normal positi circuit ofthe the shaft reaches its lowest pos1t1on.- As a further result; of thedeenergization of relay 101 the holding circuit extending back to theselector E and the line switch Ctis broken. As a result the switchingrelay.

- volved in th '58 at the selector E is denergize'd to close a circuitfor the release 111 S61 the bank, wh e apparatus -ine connection willhave been restored to norma position.

In the foregoing it has been-assumed that' the called line was idle whusy signal to the calling subscriber. 'In his is done it will foregoingparagraphs,"was in use. Under these circumstances there is a t e lowertest contact of ciated with the called line either t e normalconductor-210 bank multiple. when the slow acting relay gized at the endof the second series of impulses directed to the connector F that theprivate magnet 108 is'not-denergized as is the case when the calledlineis idle but is held ing path: grounded busy test contact, private ortest wiper 171, side switch :wiper 115 in second position, contacttrolled by armature 135 of test 'winding of the said test relay, contactspringscontrolled by the armature ot'- the rotary n'iagnet 111, restingcontact "of spring 132 and the said relay 106,

in second and 173 armatures spring contacts o f substation. A

up by current flow over the followsprings con H g a ground potentialupon sis a the side switch wipers are locked and at armature1,;6'connects'a lead from the busy sigrialing malzhi'nc "Q" to the lowertalking conductor. A distlnctlvc signal is thus transn'litted to thecalling subscriber vto inform him that,the desired line is for thepresent inaccessible. As is usual under such ciremnstances,-the callingsubscriber will then replace his receiver whereupon the automaticswitches arerestored as hereinbefore described.

Alltwo bell-stations are called from the second group of connectors likestation A l. 5 The one bell stations, however, are called from the firstgroup of connectors which have associated With them the ringingequipments shown in Fig. 5. Considering station A which We may assume tobe a one hell. 0 33 cycle station, the number of this station will be18-12 and connection may be extended thereto in substantially the samemanner as above described; except that the selector E, being operated inaccordance with the digit 1 rather than in accordance with the digit 2,selects an idle connector in the first group instead 01 an idleconnector in the second group. nector is of course the same as has beenalzc ready described and the only other difference occurring in theestablishment. of the connection which needs to be mentioned is thesubstitution of the one hell signal for the two bell signal. This itwill be readily understood is accomplished by the use of a singlesegment 1n the common rmgmg'mterrupi'er as 18 shown clearly in Fig. 5.

There is nothing unusual in the manner of extending connections tostraight or four party line stations and consequently no detailedexplanation will be given.

Having described the operation of the apparatus in completing localconnections I will now explain how connections are ex- ,35 tended fromthe local or mixed service exchange to a distant automatic exchange asfor example the vexchange Z (Fig, 1.). The call number for each of theexchanges to which trunk connections may be extended is 40 determined bythe group of connectors from which the trunk lines are accessible and bythe location of the first trunk" line in the banks of the connectors inthe group It follows therefore that sincethe trunk lines extending tothe exchange Z terminate in the last four contact sets in the tenthlevel of the second group of connectors, the telephone number to hecalled in order to extend a connection to an idle one of these trunklines the number 207. For convenience it will be assumed that thesubscriber at substation Adesires to obtain connection with somesubscriber at the exchange Z, and it will be further assumed that thefirst three .55 of the trunk lines which extend to the exchange Z arebusy. The operation of the line switch Cf and the operationof the firstselector E responsive, respectively, to the removal of thereceiver andto the calling .ot' the first digit of the number are the same as wasdescribed in the explanation of the establishment of a local connection.Like wise the "operation of the connector F in response to the callingof the digits 0 and 7' is precisely thesame as has already been deareextended by direct metallic The operation of the selected con-- tion;

scribed except of course that it is new heir operated to a differentlevel and to a diffe ent contact set in the selected level. in he casenow under consideration, however a: to; the connector operated toestablish connection with the first trunk line of the de sired group, ifthis first trunk line is busy it is necessary to select an idle trunkline of the group, and thereafter a switching operation is performed bywhich the line conductors connection through to the line conductors ofthe leoted idle 'runk line. These op actions will. now be described.

ii We assume as before me *ioned first three trunk lines wh terminatespectively in the seventh eighth and ninti': sets of contacts in thetenth l are in there will be a ground potential upon both the upper andlower test contacts of each contact set. It follows therefore that whenthe connector F is operated to Wipers 170 to 173, inclusive. intoengagcin with the seventh set of contact in. the ter level and the slowaction scri delinergizes at the end of the final so, .es oi? controllingimpulses, a circuit will. be tablished through the test relay 1% and theprivate magnet 108 as follows: ground on the lower test contact thescvemu contact set in the tenth. level, t-cst wiper 1T1, sine switchwiper in second position. co tact springs controlled by armature .nd ingof test'relay 106, contact spi' con trolled by the armature of the rotarnet llh res'ting contact of spring; 132 and the said spring, and thewinding; of the i 31* rate magnet to battery. By the establish.

ment of the above circuit the rivate on: net 108 is maintained eneryria-4. thus ing the side switch wipers in second. The test relay 106energized in series with the private magnet and upon at tracting itsarmature 133 COlYlPlQlTQSiL circuit for the rotary magnet 111 asfollows: ground on the upper test contact of the seventh. contact set inthe tenth level, test wiper 1Y0, armature 1333, contact spring windingof the rotary magnet 111 and the side switch Wiper 11.4: to battery. Bythe operation of the rotary magnet the connector wipers are advanced onestep into engagement with the eighth set of contacts in the tenth level:Near the end of its stroke the armature of the rotary magnet connectsground i to the private magnet and at the same time breaks theenergizing circuit of the test lay 106, the test relay accor ingly beingenergized. the falling back oi? the test relay the circuit or the rotay" magnet is interrupted and the magnet therefore lcenergized. It beingassumed that the ii-n1 line terminating in the eighth contact is air-3obusy, the former circuit through the test relay 1% and the private mag eninth set of contacts.

I sutne 'to beidle.

- follows: ground at and its worlnng"contact and the lower wmd-.

now be reestablished andthe rotary magnet.

will again be energized to advance the c 0n- .nec tor wipers intoengagement with the The ninth set of com tacts'being also busy the sameoperation is again repeated and the. wipers of the connector areadvanced into engagement with the tenth set of contacts which we willas- VVhen the rotarymagnet deinergizes for the last time, since there isno ground potential upon the test contact with which the wiper 171 isnow in engage ment, the test relay 106 will not again be energized andthe private magnet 108 will be permitted to de'e nergize. By this latteroperation the side switch vanced inthe'usua l manner to their thirdposition.

By the advance of side switch wipers 115 and 113 to their thirdpositions a circuit is completed for the switching relay 101 as-fol-.lows: groi nd at G side switch wiper 115'- in third position, testwiper 171, conductor .201. contact pointv246, spring 245, conductor 200,resistance 204, test wiper 170, armature 133 and its} resting con tact,oif normal contact-145 (closed only on the tenth level), winding of'relay 101, and the side switch Wipe1n113 to battery, Upon theenergization of the switchingrelayrml a' circuit is completed tor'thering. out oii' relay. 107'. as i G contact spring 121 111g of the relay107 to battery. Ground at i selector G fis alsoconnccted'by way ofcontact spring l-21-'an'd armature 120 to conductor in order mguard'against the release of'the I arid the line switch (I -upon thedecnifgization of relay 104: which instant later. Relays 101 and 107being in energized position a direct metallic connec tion has beenestablished from conductors and 94 byway of armatures 116 and118200,"thereby maintaining connection of relay 101,-armatu res 137 and 138of relay 107, armatures 140 and 141 of private magnet 108 and linewipers 172 and l73etothe' trunk conductors 202 and 203, respectively.

It follows therefore that the line relay 22 7 of the repeater M which isconnected in bridge of conductors 202 and "203 in series withthevbattery will be energized over the calling subs'cribers loop;therebyclosing at its armature 233 an energi-zing circuit for the slowacting relay 226. Relay 226, upon energizingin turn, completes a circuitfrom ground G which extends by way of-armature 232 and the winding ofslow acting. re-

' la 7 225 to battery. Relay 225', upon energizing, has the function ofbreaking, the connection between conductors 200 and 201 and ofconnecting ground G? to the conductor cuit of the switching relay 101 ofthe con nector F? independent of the former ground wipers are adtors 265and 266 with the result that theli'ne .to operate the dial of hisaccordance with the digits in. the telephone OCCllI'S an 'pleted. Thebell the energizing c1r- -bywayof the lower test wiper 171. As a furtherresult of its energization relay 225 completes a control-circuitextending to'thc distant automatic exchange Z which maybe tracedpsfollow-s: ground at G,winding oi the has rel: 267, resting contact ofarmature 2799 and tie Said armature, left hand windings of repeatingcoil R in parallel. line conductors of trunk line (3 in parallel, righthand windings of repeating coil 'R in parallel, armature 231 and itsWorking contact, working contact ofv armature 234 and the said armature,and the resistance 247 to battery. The line relay 267 is accordinglyenergized and couipletes air energizing circuit for the'slow actingrelay 268 which relay, upon energizing in turn, connects ground G" byway of its armature 274 to the conductor 263 in order to make the trunkline 6 busy at the exchange Z. As afurther resultof the operation ofrelay 268 the right hand windings of the repeating coil R are connectedat armatures 273 and 275 to the conductors 2.65 and 266 respectively.Since the line relay 267, in addition to closing the circuit of therelay 268,also short circuits the condenser which is connected in serieswith the two right hand windings of the repeating coil R, a conductivebridge is now closed across the con'ducswitch in which these conductorsterminate is operated in the usual manner to selectan idle selectorswitch.

The calling subscriber may now proceed calling device in number of thesubscriber in the automatic exchange Z with whom he deslres' to obtainconnection, thereby producing successlve series of interruptions in thecircuit ofthe line .relay227 of the repeater M. During each series ofinterruptions the line relay 227 is deenergized a number of times andthereby interrupts the control. circuit ineluding the line relay 267 ofthe repeater.1l0

M, this latter relay being likewise de'-nergized intermittently tointerrupt the bridge across the conductors 265 and-266. Thus it will beseen that the interruptions produced by the calling device at. thecalling substation will be repeated by the line relays 227 and 267. ofrepeaters M and M'in order to effect, the operation .of a series of.switches in the exchange Z, whereby theconnection" to the line of thecalled subscriber is comat the called substation is thengrungautomatically in the usual lnanner and when the called subscriberresponds conversation may be held as desired. There being nothingunusual in the signaling 01* 1:!6

talking circuits no detailed explanationneed be given. i 'j. f When theconversation is finishedboth subscribers will hang' up their receiver.-

When the receiver at substatioh A isre- 113011 placed the line circuitis broken and the line relay 227 at repeater M is accordinglydeenergized. The deener'gization of relay 227 opens the control circuitincluding the line relay 267 of repeater M and .the resulting vfromconductor 200. By the removal of ground from conductor 200 theenergizing circuit of the switching relay 101 of connec tor "F is brokenand inasmuch as relay 25 is slow acting this circuit remains open longenough to permit relaylOL to deiinergize. By the retraction of armature120 of relay 101 ground G? is disconnected from the holding conductor 93and/is connected instead to'the release magnet 100, thereby causing therelea'seof theconnector F It should be mentioned tl'iatithe connector isreleased and the side switch Wiper 115 restored to first position beforethe slow acting relay 225 at the repeater/M has had time to decnergize.By the ren'i'oval' of ground from the holding conductor 93 the selectorE and the line switch C are restored to normal in the usual manner.

In calling into a group of trunks on the tenth level, if all the trunksin the group are busy the connector in use will stop on the last trunkanyway, because of the resistance as 204 for instance which is includedin series with the private normal conductor associated with thelasttrunk, this resistance being high enough to prevent the opcration of therotary magnet. In such a case the test relay of the connector and theprivate magnet are maintained energized until the connection is releasedand the calling subscriber will hear the busy signal when he places thereceiver to his ear.

It is understood that the trunk lines connecting the exchange X or mixedservice exchange with the automatic exchange Z are two way trunk linesand are adapted to handle connections in either direction.

To provide for handling calls from the 6X" change Z to the exchange Xthe group of four trunk lines may terminate in a selector level in theformer exchange; and considering the particular trunk line number Gwhich is shown in the drawings, the conductors 262, 263 and 264'mayterminate in the first set of contacts of the level which is reservedfor this purpose. Suppose now that a subscriber in the exchange Zdesires to obtain connection with a subscriber in i We assume that thetrunk line number 6 is the one with which connection is established theline relay 269 will energize as soonlas the connection is completed andWill in turn complete a circuit for theslow acting relay 270. Relay 270,upon energizing, connects ground G to the conductor 263 in order tomaintain the operated selector or selectors in operated position. By theenergize tion of relays 269 and 270 a control circuit including the linerelay 229 in the repeater M is completed as follows: ground at G,winding of relay 229, resting contact of armature 231 and the saidarmature, right hand windings of repcatingcoil R in parallel, lineconductors of trunk 'line number 6 in parallel, left hand windings ofrepeating coil B in parallel, armature, 279 and its workingcontactavoiking contact of armature 277 and the said armature, andthe-resistance to bat tery. The closure oi the above control circuit isfollowed by the encrgization of relays 229 and 228m the repeater M thelatter relay being cliective to ground conductors 200 and 20l andthereby render the trunk'line busy to connector switches such as theconnector F in the exchange X. Relays 228 and 229 also close a' bridgeacross the conductors 24.1 and 24-2 tooperate the line switch (7 for thepurposeot selecting and connecting with an idle selector switch. N owwhen the callingsubscriber in the distant automatic exchange operatesthe dial of his calling device the interruptions of the line circuitwhich are produced are repcated by means of line relays 269, and 229,and thereby cause the operation of the selectcd. selector and aconnector in the 0X- change X in order to complete the requiredconnection to the desired subscribers line.

Since thc connector switch under these cir-- cumstanccs opcratcscxactiythesame as was described in thc/cxplanathm of the .cstablishmcnt of alocal connection no further details need be given. When the receiver isrcplaccd at the distant exchange Z. the

The I exchangeis being called. No switching.

through operation takes place, however, for

the of]? normal contact 145 is closed when on the tenth' level and anextra digit must be called to operatev the frequency selectlng switch Sas when calling a local line. In accordance with the location of the Yexchange trunks in the drawingthe proper digits to 'be called would bethe digits 2, 9,14: andone a'dditional digit,

When the operator plugs in to answer the which the operator p theexchange X' and therefore are entitled It may be, however, who arefurnished her to rebate the charge. Ordinarily of course all calls fromthe exchangeX to the manual exchange Y willhave to be-paid and it is theduty of the operator at the latter point to charge all incoming callsfrom the exchange X to'the proper parties. that certain subscriberstelephone service from the exchange X are in reality located about asclose to the'exchange Y as they are to to, communicate-withsubscribers-in the exchange Y free of charge. In order to notify theoperator at the manual exchange when she is being called by an X'exchange subscriber who is entitled to free service, specialequipment-is provided comprising a signal ing device K at the exchange Xand comprising also an induction coil such-as'the induction will whichis associated with each .of the connectors, such as the connector FIn-the exchange X the'holdin windings of the line switchesassociate,with lines whose subscribers are entitled to free calls to theexchangeY are not con:

nected direct to battery but on the contrary line are located near theend ofithe line switch C is disconnectedfrom terminal extend to batterybyway of the secondary; winding of the inductioncoil of the signalingdevice K. Thus if we assume for the sa e of illustration that the partyline corn prisin conductors 3O and31 extends in the direction of theexchange Y as shown in the drawing and that the subscribes n'thisline itmay be that these subscribers-will ge'Y. To

. 49 and is connected insteadjto terminal 48.

- and conductor F to ..When connected in this 'way if a connection "isextended by means of .the selector E the manual exchange Y a distinctivetone produced by the signaling device K will be transmitted by way ofthe holding conductors 61 and 93, the Induction preferably the digit 2.

key the relay certain calls tonotify is nothing particularly be en-' theoperation is set is preferably connected directly in of the trunk linein order to operate the ring out off relay 107 .and thereby stop theringing operation. It follows that'immediatclv upon the energization ofrelay 107 the bat tery supply relay 102 will be energized and .the' lefthand winding of the induction coil P will be short circuited.

The operator at the manual exchange,

however, may have a condenser connected in series 'with her head 1 setand normally short circuited through the contacts of a special-listeningkey. lVith this arrangement the operator is instructed to listen in withher special listening key on all calls incomin WVhen the speciallistening key is thrown the condenser will becut in series with theoperators head set and the battery supply rela 102 at the exchange X beeenergized. Under these conditions the operator will be able to'hear thetone if it is present on the line and will, rebate the charge for thecall accordingly. Since there difficult in the design of the operatorscord circuit it has not been thought necessary to illustrate the sameand any suitable arrangement may be used instead of the one hereinproposed. Attention will now be directed to the ring back equipmentthrough the medium of" which the party line subscriber is enabled tosignal another subscriber on his own line. This equipment comprises aplurality of ring backswitches one of which is the switch H (-Fig; 4)and the common rotary ringing switch I. In general the method ofhandling reverting calls in my present system is similar to the methoddisclosed in the patent to .Hovland No. 1,158,221., wherein there isdescribed a revertin call or ring back system in which the callingsubscriber by manipulating his dial in accordance with the proper digitsoperates a ring backswitch at the exchange to select the two frequenciesof ringing current which corresponds to the calling and calledsubstations.;- The calling subscriber then hangs up his rejieiver,whereupon mechanism in the'ring back switch is operated to effect theapplication of the selected ringing currents to the calling linealternately. The called subscriber is' thussigna led as usual;.while thecalling-subscriber is also signaled so that he may know that proceedingproperly and also that he may know by'the-cessation of the ringing ofthe response of. the called party. Owing -to the fact that in'thepresent system the selective ringing is accomplished by a combination ofthe one and two bell principle, ratherAthan on the harmonic principlealone as in the Hovland system, the apparatus and circuits employed areradically different although the general from the, exchange X.

will therefore tin * swi h. as

"- horizontal principle of operation is substantially the same. 4

Each party line subscriber is supplied with a list of special numberswhich are to be used in calling the other parties on his own line. Thesenumbers of course conform to the wiring of the banks of the ring hackswitches, which it may he stated is largely an arbitrary arrange:uentalthough considerable care has heentaken to devise as simple schemepossible. The bank wiring of one of the ring back the wiring of theringing switch I shown complete in here: which correspond to the wiriirgshown are given in the table below.

Calling; a aziun. Caller Motion. Nmnbcr.

it caliing .21 or A? A 31 a an; A" A A [t 317 A A. 31.9 A. A 310 A A 321A A 823 [a A 3-27 A. 329 $1. 320 u A A. 333 A 335 A 33? A" 339 f 330 it:an A 343 A 345 A 34:7 A 3&9 is c are ii 351 A, f: t-a A 355 A A 357 Theoperation of the apparatus in a rell will now he explained, it beingthis purpose thatthesuhscriher A (Fig. desires to call the su'oscimer atsuhstation A". By referring to the tahic it. will he seeirthatithenumber to he called in this case is the number Upon the removal of thereceiver at Sill!- station It the line switch {1* is operated in themanner already explained to extend. the line comluctors and 31 to thetrunk conductor rrl ch terminate in an idle selector zed to he theselector id, in to the calling oi he first digit 3 her the firstselector operated. .iaft in the usual manner until 5 so, 81 and arriveat the third icvel of bank contacts, after which the wipe;

switches and Fig. "l and the special call hum-- the wipers areautomatically rotated to pick out an idle set of contacts in theSelected level, Assuming that the contact setcomprising bank contacts89, 90, and 91 is the set selected, upon the energization of theswitching relay 58 the line conductorsjare further extended intoconnection with trunk conductors 98 and 100 which terminate in thewindings of the line relay 300 of the ring hack switch H (Fig. 4:). Theline relay 300 is accordingly energized over the two sides of thecalling line in series in the usual manner and upon attracting itsarmature 316 cou'iple-tes slow acting release relay 301. Upon energizingin turn, relay 301 connects ground G to the holding conductor 99 at itsarmature 317, thereby completing the usual holding circuit by which theselector E and the line switch C are maintained in operated position. I

The calling subscriber at substation A. may now operate his callingdevice in accordance with the second digit 1 of the number, therebyproducing a momentary interruption in the circuit of the line relay 300.The line relay 300is accordingly deenergi' 'ed momentarily and transmitsan impulse of current to the vertical magnet 306 over the following pathrground at G, armature 316 and its resting contact,.armat-ure 318 andits working contact, winding of the slow acting series relay 302,winding of the vertical magnet 306,- and the side switch wiper 309 infirst position to batter-y. In response to this impulse of current thever 'cal magnet is operated to raise the switch shaft one step, thewipers 330 and 331 lacing thereby brought into alinement with the firsthorizontal level of bank contacts. The slow acting relay 302 isenergized in series with the'vertical magnet, and operates the privatemagnet-308 in the usual manner. Both the relay 302 and the privatemagnet are dcenergized after thevertical ope1'atioii of. the switch, thedee'ncr'gization of the private magnet being etl'cctive' tocause theadvance of the side switch wipers from first to second position.

The callingsubscriber will now operate his calling device in accordancewith the third digit 5 of the number, producing this time fiveinterruptionsin the circuit of the line relay 300. The resulting (leincrgizations of the line relay 300 now cause five impulses of current tobe transmitted through the rotary magnet 307, side switch wiper 309having been advanced to its second position. By the operation of therotary magnet 307 the switch shaft is rotated until the wipers 330 and331 come into engagement with the fifth set of hank contacts in thefirst level, those hank contacts being indicated in the drawing by thereference characters 371and 312. The slow acting an energizing circuitfor the of the ring back switch-as relay 302 and the private magnet 308are operated as before and the latter upon deenergizing permits the sidewitch wipers to advance to their third and final position.

The calling subscriber will now hang up his receiver.

Since this operation opens the line circuit the line relay 300 isde'cinergizcd and closesa circuit for the relay 312- as follows: groundat G, armature 316 and 0 its resting contact, armature 318 and itsworking contact, Winding of the slowacting Series relay 302, winding ofrelay 312, and

the side switch .wiper 3.09 in third position to battery. Uponenergizing, relay 812 com- -wpletes a newcircuit forthe slow actingi-elease relay 801 as follmvszgi'ound at G, ofi' normal contact 311(closed at the first Upward -movement of the switch shaft),

armature- 315 and its right hand working contaet, armature 321 and itsresting c011- tact, and the-winding of relay 301 to battery.. Inaddition relay .312 closes a circuit' for starting the operation of theringing SWltCh' I which extends over the following pathzg'round at G",ofi' normal contact 311,

armature 315 and its left hand working contact, conductor 352, bankcontactnormally Y engaged by the wiper 355 of the ringing switch I, thesaid wiper 355,-contact springs of the interrupter relay 351, andthrough the saidinterrupter relay-B51 and theniotor i'nagnet 350 inparallel to battery. The,

motor magnet 350- thusreceives an impulse of current by which it isoperated to ad-J 5 vance the wipers 354, 355 and 356 of the ringingswitch into engagement. with the second set of bank contacts. Since allthebank contact which are adapted to be engaged by the wipeeflofi,except the first,

40 are multipled together and connected to I ground G it will be evidentthat a. circuit has now been establishedfor the motor inagnet'350 andthe interrupter relay 351, where- 'by the ringing switch I will. becaused to advance its wiperssuccessively into engagementwith all of thecontact sets in its bank finally returning to theirfirst' or normalposition. In other words, upon. recei\'ing .the initial starting impulsethe switch 'I i makes a complete revolution and returns to normalposition. Of course if the relay switch I will then immediately start'on a second revolution and is still energized the will thus rotatecontinuously as long as the conductor 352 is grounded I When the wipers354, 355 and. 356 of the bank contact 37201 the ring back switch, wiper331, upper winding of bank contact 367,

the ringing relay 30 i and a signaling circuitfor operating the linger.

at substation A over the followin )ath:-

ground at G, ringingcurrent generator AC the resistance lamp, bankcontact. 362,

wiper 356, conductor working contact of armature and the said armature,working contact of armature '313 and the said armature, conductor 98,bank contact Sf), wiper 80, contacts controlled by the switching relay58 of selector E, bank contact 4+1, spring 40, line conductor 30,through the ringers at all the party line substations in parallel,conductor 31, spring ell-3, bank contact 17, contacts controlled by theswitching relay 5S, wiper 82, bank contact 91, con duetor 100, armature314 and its working contact, winding of ring cut oil relay 303 andthrough the exchange battery to ground G As soon as the wipers of theringing-switch advance to the next set of contacts the ringing relay 30l is of course deenergized and the above described. signaling circuit isthe ringing relay 304; completes broken but is immediate] com ileted aain when the wipers arrive at the contact set comprising ba'nk contacts363, 361 and 365, these latter contacts being connected inmultiple withthe. contacts 360, 361 and 362, respectively. It will be seen thc irthatthe ringer at substation A will be operated twice for the ringer at thissubstation is tuned to respond to the 3S cycle ringingcuri'ent delivered by the ringing current generator AC Station A'liciiig a two-bellstation the two rings received-serve to notify the subscriber that he isbeing called. When the wipers of the ringing switch arrive atthe'contact set comprising bank contacts 366, 367 and 368 a circuit iscompleted for the ringing relav 30-1 over the following path: ground at(l wipers 355 and 354, bank contact 366, conductor 3T0, bankcontact-371, wiper 330, relay 304-.and the side switch wiper 310. Theringing rclay30l is accordingly again energized and the signalingcircuit is again completed. This time, however, the wiper 356 being inengagement with bank contact 368 the 16 cycle ringing current generatorAC is included in the circuitinstead of the 33 cycle generator AC Itfollows accordingly thatthe ringer at the one bell 16 cycle station A:will be actuated to calling subscriber that the-signaling opera. tion isproceeding satisfactorily. In case the called not answer immediately theabove described Q l 0 I A l signaling pcrations will be repeatedduringthe second revolution of the ringing switch I and will cont nue tobe rep'eated at interlower winding of the ringing subscriber atsubstation A does notify the I ca-ls "until a respon'se is made or untilthe calling subscriber again removes his receiver, at which t me arelease will occur as presently set forth. t is to be noted that in thesilent periods between rings the conductor 98 1s connected to groundiii; in order that the ring out 01f relay 303 may be operatedimmediately upon the removal of the receiver at the called substationwhether the receiver 'is removed during a ringing period or a silentperiod. The ring cut off relay of course is so adjusted that it will notenergize until the receiver is removed from the hook. But as soon as thesubscriber at substation A answers the said relay 303 operates, eitherby current from the exchange battery alone or by current from the exchange battery and the generator in use in series, and closes a asfollows: ground at G, ofi normal contact 311, armature 315 and its righthand working contact, armature 321 and its work ing contact, and thewinding of the said relay 303 to battery. In addition by attracting itsarmature 320 relay 303 disconnects ground G from the holding conductor99, thereby breaking the holding circuit by which the selector E and theline switch G are being maintained in operated position. The line switchC and the selector E immediately release and restore to normal in theusual manner. But since the receiver at substation A is oii thehook theline switch C will at once operate again to extend the line conductors30 and 31 again into connection with the line relay of the selctor E. Atthe ring back switch H. the ring cut oil relay 303 also opens thecircuit of theslow acting release relay 301 and this relay upondetnergizing completes a circuit in the usual manner for the releasemagnet 305. The operation of the release magnet restores the ring backswitch to normal position and the locking circuit of the cut oii' relay303 and also the circuit of the release magnet are broken when the shaftreaches its normal po sition. The ringing switch Iwill complete therevolution upon which it is engaged and will then stop unless some otherring back switch similar to the switch H is in use. \Vhen the callingsubscriber at substation A notices the fact that his bell'has stoppedringing he willknow thatthe called party has answered and he willtherefore remove his own receiver also and converse as de-' Tal king*current for the transmitters sired.

at the calling and called substations is supplied from the relay 5Uandthe im )edanc-e coil 51 in the. first selector E.

receiver are replaced on the line the line switch (7 is restored in theusual manner.

What I claim as my invention is:

1. In a' telephone system, an automatic.

switch, a closed control circuit for said switch including a source ofcuri'entmneans for producim; a series of interruptions in said circuitto control the operation of said locking circuit for itselfv ion theautomatic means for increasing. the currentv how in said circuit aftereach interruption to a point above normal in order to facilitate theenergization of said relay after each deenergizatlon.

3.111 a telephone system, an automatic switch and a closed controlcircuit therefor including a battery, means for producing a series ofinterruptions in said circuit to operate said switch, and means in saidswitch for automatically decreasing the resistance of said circuit whilethe switch is operating.

4. In a telephone system, an automatic switch and a closed controlcircuit therefor including a battery, means for producing variableseries of interruptions in said circuit to directively control theoperation of said switch, and means in said switch for automaticallydecreasing the resistance of said circuit while the switch is operating.

5. In a telephone system, an automatic switch. and a closedcontrolcircuit therefor including axbattery, means for producing a series ofinterruptions in saidcircuitto opcrate said switch, and means in saidswitch for automatically lowering the impedance of said circuit whilethe switch is operating.

switch, and means in said switch for auto.-

matically lowering the resistance of said circu-it during thetransmission of impulses. I

S. In a telephone system, an automatic switch and a control circuittherefor, means for transmitting directive current impulses over saidcircuit to variably operate said switch, and means in said-switchforautomatically' lowering the impedance of said circuit durin thetransmission of impulses.

9. In a telephone system, an automatic witch and a control circuittherefor, means for transmitting directive current impulses over saidcircuit to variably operate said switch, and means in said switchfol-"automatically lowering the resistance and impedance of said circultduring the transmission of in'ipulses.

10. In a telephone system, a trunk l1ne,'a

main progressively movable switch indiopen connection in said conductor.

., cess'ible to said switch, two series of test conline, the twocontacts of certain ll. In a telephone system, a plurality ofsubscribers lines, a group of trunk lines, means foroperating saidconnector to establish connection with a desired subscribers line, orltoselect and establish connection with an idle trunk line, an operatingmagnet incl udedin said-means, and a relay operating as a busy testrelay when a subscribers,

line is selected, and operatingas a stepping relay for said magnet'whenan idle trunk is beingselected.

12. In a telephone system, an automatic connector switch, a pluralityof, trunk lines accessible to said switch and divided into groups, apair of test contacts for each trunk pairs being iconductivelyconnected, a pair oi test wipers for said onnector, and associatedtesting mechanism and circuits in said connector suchthat the divisionof said trunk-lines into groups is determined by the abscnceofconductive connections "between the pair of test 'COIItQiC tSILSSOClQtBQwith the last trunk line of each group.

13. In a telephone system, an automaticconnector switch, a plurality oftrunk lines accessible to said. switch anddi'vided into groups, a pairof test contacts for each trunk line conduotively connected,a'resistance included in certain of said connections, a pair of testwipers coiiperating with said pairs of contacts, and testing mechanismand circuits-associated with said wipers such that the division of saidtrunk'lines into. groups is determinedby' the presence of a resistancein the connection between the test contacts associated'with thelastft'ru'nk line of each group.

14;. In a telephone system, anautomatic connector 'switch,"a group of-'trunk'lines actacts in said connector, there being a test contactineach series for each trunk line, conductive connections between. thetest contacts associated with'each trunk line except the 7 last, meansfor operating said connector to connect with the first of said trunklines if the sanicis idle a test wi )er for each series of testcontacts, and means controlled by the coijperationof said wipers withsaid test .contacts for causing said connector to automatically selectan. idle trunk line-if the first is busy. v h

15. In a telephone system, an automatic connector switch, a. group oftrunk lines accessible-to said switch, two series of test contacts insaid connectonthere 'beinga test contact in each series for each trunkline,- conductive connections between the test contacts associated witheach trunk line except the last, means for operating said connector toconnect with the first of said trunk lines if "the same is idle, a testwiper for each series of test contacts, and means controlled by thecooperation of said wipers with said test contacts for causing saidconnector to automatically select an idle trunk line if the first isbusy and eifective'to stop said 0011- nector on the last trunk linewhether. the

same is busy or idle.

16. In a telephone system, an automatic connector switch, a pluralityof-groups of trunk lines accessible to said switch, two series of testcontacts in said connector corresponding to the several trunk lines,conductive connections between the two test contacts which areassociated with each trunk line, except that between the test contactsassociated with'the last trunk line of each group the connections areomitted,"

means for operating, saidconnector to connect with the first trunklineof any group I a test wiper for each if the same is idle,

and means in said con= series of test contacts,

'nector coiiper'ating with said wipers to cause said connector toautomatically select an idle trunk line if the first is busy.

17; In atelephone system, an automatic connector switch, a plurality ofgroups of. trunk lines accessible .to said switch, two' series of-testcontacts in said connector. cor: respondlng to the several trunk l1nes,-con-' Y I ductive connections between the twotest contacts which areassociated with each trunk line, except that between the test contactsassociated with the last trunk line of each group the connections areomitted, means for operating said connector to connect with the firsttrunk line'of any group if the same lot .is idle, a test wiper foreach-series of test contacts, and means in said connector (:0

operating with said wipers to cause saidconnector to automaticallyselect an idle trunk lineif the first is busy and efiective to'stop saidconnector on the last trunk line of the group whether the same is busyor idle.

18. In a telephone system,'an automatic connector switch, a group oftrunk lines 210-.

cessible to said switch, two series of test con-- ta'cts in saidconnector corresponding to the several trunk lines, conductiveconnections between the two test contacts associated with eachtrunkline, a resistance included in the connection between the test contactsasso-

